The present invention is related generally to the communication of information and, in particular, to methods and apparatus for the encoding and/or the decoding of analog data to reduce the bandwidth required for transmission of the data and/or to improve the usefulness of the data to a user thereof.
The communication of information from one location to another generally requires the utilization of a certain amount of bandwidth on the transmission medium. Because the bandwidth of a medium is generally fixed and limited, various systems and methods have been developed to reduce the bandwidth required for a particular type of information. For example, in video applications (generally television images), it is known to compress the moving image data by using various coding techniques to reduce the interframe and intraframe redundancy in the data. A typical visual image contains areas in which the pels (which represent the visual data) do not substantially change over a portion of the image. In such a case, the user does not need to transmit each pel separately but may transmit the data describing one of the similar pels and data describing the area over which that pel value is valid.
In a similar fashion, the set of pel values for an image region may, even if widely varied across the region, remain relatively constant over multiple occurrences of the image. Rather than repeatedly transmitting values for these pels, the data may be compressed by transmitting both the value of each pel (represented by its red, green and blue components) and a value indicating the number of occurrences of the pel values (say N) The receiver of the compressed data then reconstructs the original by expanding (or repeating) the pel values the number of times (N) indicated. In such a compression scheme, the amount of data needed to be transmitted over the medium is thus reduced by a factor of N (approximately).
Most compression techniques take advantage of the fact that the processing speed of modern computing devices is high, while the transmission speed available for data generated or processed by the devices is quite limited. The compression schemes illustrated above clearly require more processor capability than one that merely sends the xe2x80x9crawxe2x80x9d data; however, it enables the sending of more images over a given bandwidth (or the use of less bandwidth to send the same number of images) than by sending the xe2x80x9crawxe2x80x9d data. Such conventional compression schemes, however, do not remove all of the data redundancy present in moving image data.
In systems which transmit intrinsically analog data in digital form, the data is often processed in successive xe2x80x9cframesxe2x80x9d, where each frame contains the digital representation of an analog signal over a definite time interval. In most cases, there is a considerable redundancy from one frame to the next. For example, in consecutive frames in a television signal, frame content changes only where there is movement within the image scene or by the television camera itself. Successive frames are largely determinable, from the immediately preceding frames. Interframe compression schemes take advantage of this redundancy to reduce the transmission bandwidth required.
For example, in one prior art system which is the subject of pending application Ser. No. 261,979, filed Jun. 17, 1994, assigned to the same assignee as the present application, bandwidth is reduced by comparing successive frames so as to transmit only changed portions. Because such a system does not re-transmit the unchanged content of previous frames, bandwidth is on average substantially reduced.
It is also known in prior art systems, described in U.S. Pat. No. 5,128,776 assigned to the same assignee as the present application, to reduce transmission bandwidth by transmitting only portions of the image which a user has identified as being of interest. For example, in a complex battlefield scene, a user may select to transmit only the changed image data in the vicinity of a particular truck or tank.
Still other prior art video systems reduce bandwidth by reducing the frequency of motion frames, from, say, the U.S. commercial standard of 30 frames per second, to as few as 2 frames per second. The chief cost of this reduction is image flicker and resulting viewer discomfort.
It is known in the prior art to attempt to smooth successive frame signals by interpolating data at a pel level on the basis of a predetermined mathematical relationship. Because moving image data has spatial dimensions as well as a temporal one, such interpolation, however, cannot accurately reflect the actual movement of the source or satisfactorily display smooth and realistic changes between frames.
Similarly to the case for video, known methods and systems of encoding for transmission of both musical and spoken audio do not exploit the recurring patterns of frequency, dispersion, and amplitude in an audio signal. In contrast to video, audio exhibits an additional anomaly related to content. A pianist may translate a score into sound at a rate of no more than a dozen notes per second, some hundred data bits of printed notation. A full second of human speech comprises only some two words, or forty bits as mapped against a dictionary. Despite these modest demands, digital audio techniques are hard pressed to support comprehensible speech or listenable music at bandwidths two orders of magnitude greater.
It is apparent that conventional video and audio compression methods and systems do not take full advantage of pattern repetitions in data and take no advantage of the primary information content of target data.
It is accordingly an object of the present invention to provide a novel system and method for transmitting data with reduced bandwidth requirements while maintaining accurate data.
It is another object of the present invention to provide a novel system and method for modeling the apparent content of time slices or frames of audio, video and other data, and transmitting data which enables reconstruction of the data from the model.
It is another object of the present invention to provide a novel system and method for communicating visual data without flicker and with reduced bandwidth requirements.
It is a further object of the present invention to provide a novel system and method for transmitting digital data in which redundant information in successive frames is reduced.
It is still another object of the present invention to provide a novel system and method for generating from a digital signal an analog signal that exhibits changes in the underlying information at interpolated times between consecutive digital frames.
It is yet a further object of the present invention to provide a novel system and method for transmitting sequential frames of digital data based on objects found within the data.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.